Power/Performance Bits: Sept. 17

Harvesting energy from light
In a finding they believe could improve technologies for generating electricity from solar energy and lead to more efficient optoelectronic devices used in communications, researchers from the University of Pennsylvania and Duke University have demonstrated a new mechanism for extracting energy from light.

They said the process is much more efficient than conventional photoconduction, and that using such an approach could make solar energy harvesting and optoelectronic devices much better.

The work centers on plasmonic nanostructures, specifically, materials fabricated from gold particles and light-sensitive molecules of porphyin, of precise sizes and arranged in specific patterns. Plasmons, or a collective oscillation of electrons, can be excited in these systems by optical radiation and induce an electrical current that can move in a pattern determined by the size and layout of the gold particles, as well as the electrical properties of the surrounding environment.

Since these materials can enhance the scattering of light, they have the potential to be used to advantage in a range of technological applications, such as increasing absorption in solar cells.

Researchers fabricated nanostructures with various photoconduction properties. (Source: University of Pennsylvania)

The researchers said to imagine having paint on a laptop that acted like a solar cell to power it using only sunlight. These materials could also improve communications devices, becoming part of efficient molecular circuits.

Smartphone microscope
According to researchers at UCLA, your smartphone now can see what the naked eye cannot: A single virus and bits of material less than one-thousandth of the width of a human hair. The researchers have created a portable smartphone attachment that can be used to perform sophisticated field testing to detect viruses and bacteria without the need for bulky and expensive microscopes and lab equipment. The device weighs less than half a pound.

The cellphone-based imaging platform could be used for specific and sensitive detection of sub-wavelength objects, including bacteria and viruses and therefore could enable the practice of nanotechnology and biomedical testing in field settings and even in remote and resource-limited environments. These results also constitute the first time that single nanoparticles and viruses have been detected using a cellphone-based, field-portable imaging system, they said.

Capturing clear images of objects as tiny as a single virus or a nanoparticle is difficult because the optical signal strength and contrast are very low for objects that are smaller than the wavelength of light. This device includes a fluorescent microscope device fabricated by a 3D printer that contains a color filter, an external lens and a laser diode. The diode illuminates fluid or solid samples at a steep angle of roughly 75 degrees. This oblique illumination avoids detection of scattered light that would otherwise interfere with the intended fluorescent image.

Using this device, which attaches directly to the camera module on a smartphone, the researchers were able to detect single human cytomegalovirus particles, which measure about 150 to 300nm.

(Source: UCLA)

To verify results, the researchers used other imaging devices, including a scanning electron microscope and a photon-counting confocal microscope. These experiments confirmed the findings made using the new cellphone-based imaging device.